Green, 19, leaves Munich, who have brought in 18-year-old Kurt from Monchengladbach. Xherdan Shaqiri, however, has been told he is not allowed to leave the Bundesliga champions despite interest from several other clubs.

Green will spend the season at Hamburg to gain first-team experience in the Bundesliga, having struggled for opportunities under Pep Guardiola. The loan deal includes no option to make the deal permanent, according to Hamburger Abendblatt.

The United States international made his debut for Bayern in the Champions League last season, but did not feature in the Bundesliga.

The transfer has the backing of United States head coach Jurgen Klinsmann, who "is very keen on Hamburg," according to Green's father Jerry, who spoke to ESPN FC on Sunday.

"He knows the coach [Mirko Slomka]. He knows the people there. It's a great opportunity for Julian to play some games. He thinks this is going to be a good thing for Julian and the U.S. team," Jerry Green said.

However, Green will not be unveiled at Hamburg on Monday as he joins up with the United States squad ahead of their friendly against Czech Republic on Wednesday.

"He will not be here, because he travels to the national team. But he will arrive within the week," Hamburg CEO Dietmar Beiersdorfer told NDR Sportclub.